The California Regional Primate Research Center (CRPRC) is currently equipped with an ATL MK 600 which was purchased new in 1984. In order to continue to provide state-of-the-art sonographic support for a variety of NIH-funded studies, a new unit with the current technological advances is required. For our purposes, the improvements in image quality, variety of transducer options, expansion of pulsed Doppler features, in addition to the availability of color Doppler imaging (CDI) would allow us to enhance and expand our current research focus. In addition, CDI would provide an additional means for evaluating maternal/fetal/placental interactions, an area that has not been fully explored. A variety of studies related to developmental and reproductive biology using the nonhuman primate (macaque) as a model for the human are performed at the CRPRC. We have established a substantial ultrasound program specifically related to the reproductive biology of the macaque with defined growth charts for a variety of biometric parameters, methods for evaluating embryonic and fetal normal and abnormal growth and development, in addition to a number of ultrasound- guided interventional procedures for both gravid and nongravid female macaques. We have the capabilities to access both the embryo and fetus with ultrasound-guidance, thus eliminating the need for surgical procedures. These techniques and procedures are incorporated in all studies of a reproductive nature performed at the CRPRC. Our overall Center aim is to utilize the nonhuman primate as a model to investigate those areas that cannot be ethically explored in the human with the intent of applying learned information and techniques to the human clinical setting. Projects currently in progress at the CRPRC with NIH funding include: (1) studies to determine the potential pre- and postnatal bioeffects of prenatal ultrasound exposure (#HD25528), (2) mechanisms of action and effects of treatment of fetal and neonatal macaques with epidermal growth factor (EGF) (#HD24959), and (3) the development of rhesus models for in utero hematopoietic stem cell (HSC) transplantation utilizing (a) adult T-cell depleted bone marrow (#AI29512) and (b) fetal liver (#HL39875). All of the above in addition to several studies supported by the CRPRC base grant (#RR00169) and an NICHD contract (#HD3-2804) would benefit from the incorporation of a new ultrasound unit. It would provide the ability to enhance, expand, and complement our current research interests in addition to promote new avenues of focus and potential funding.